1. Field of the Invention
The present invention relates to a calibration and quantification method for gas imaging infrared (IR) cameras. The calibration and/or verification system and method quantitatively determine the performance of a particular gas imaging IR camera, and determine whether the gas imaging IR camera is in a working condition. The quantification method determines the concentration and/or leak rate observed by a gas imaging IR camera.
2. Description of the Related Art
In recent years, gas imaging Infrared (IR) cameras have become a popular tool in hydrocarbon processing industries for gas leak detection. On Dec. 22, 2008, the U.S. Environmental Protection Agency (EPA) promulgated the Alternative Work Practice (AWP) rule (40 CFR §60.18, §63.11, and §65.7) that allowed regulated facilities to use IR cameras to detect leaks for compliance with the Federal Leak Detection and Repair (LDAR) regulations. On Mar. 26, 2012, EPA proposed a Uniform Standards (40 CFR 65) that also included IR camera for equipment leak detection. Compared to the conventional method of checking equipment leak component by component using a portable flame ionization detector (FID) per 40 CFR 60 Appendix A-7, Method 21, the IR camera method can check a large number of components in the field of view at once, and therefore it is less labor intensive. It can also be used for inspection of components that are difficult to reach with conventional methods.
For regulatory applications, the operators of the IR camera are required to perform a daily camera check per 40 CFR §60.18 (i)(2). The daily check is qualitative meaning in which the operator will either “see” gas or not “see” gas. Many factors affect the camera's ability to “see” gas, such as the type of background, temperature, sunlight, camera's condition, operator's experience in interpreting IR imagery, etc. There is no standard across different facilities by which a camera can be deemed to be in good working condition. The gas imaging IR cameras require sophisticated filters and cooled detectors. A slight difference in the performance of the cooling system or the narrow bandpass filter could significantly change the sensitivity of the camera to particular compounds. The qualitative and subjective daily check that is currently performed would unlikely detect the change in sensitivity of one camera or sensitivity difference among different cameras. Accordingly, a method and system to quantitatively determine the performance of a particular gas imaging IR camera are needed.
A limiting factor for the adoption of gas imaging technology as a complete replacement for conventional methods of leak detection is the inability to provide a quantitative measurement. While gas imaging cameras have been accepted as an approved AWP, the rule still requires inspection by conventional methods at least one quarter per year. Accordingly, a method is needed to determine a quantitative measurement of concentration and/or leak rate using gas imaging cameras.